Turbine engines are used as the primary power source for various kinds of aircraft and other vehicles. The engines may also serve as auxiliary power sources that drive air compressors, hydraulic pumps, and industrial electrical power generators. Most turbine engines generally follow the same basic power generation procedure. Compressed air is mixed with fuel and burned, and the expanding hot combustion gases are directed against stationary turbine vanes in the engine. The vanes turn the high velocity gas flow partially sideways to impinge onto turbine blades mounted on a rotatable turbine disk. The force of the impinging gas causes the turbine disk to spin at high speed. Jet propulsion engines use the power created by the rotating turbine disk to draw more air into the engine, and the high velocity combustion gas is passed out of the gas turbine aft end to create forward thrust. Other engines use this power to turn one or more propellers, electrical generators, or other devices. Because fuel efficiency increases as engine operating temperatures increase, turbine engine blades and vanes are typically fabricated from high-temperature materials, such a high-temperature metal alloys.
As gas turbine engine performance requirements continue to push for improved fuel economy and power density, the speeds and temperatures of the engines continue to rise to meet the thermodynamic requirements associated with the improved engine cycles. Thus, improved materials are needed to maintain component life at these elevated stress and temperature levels. It is known in the prior art to use ceramic reinforced titanium alloys for such applications. However, known prior art methods for the manufacture of such alloys, which utilize mechanical press and sintering, or hot isostatic press (HIP), or even laser engineered net-shaping (LENS), do not result in a metallurgical microstructure for optimal material properties and do not achieve an acceptable final component shape. In addition, these prior art fabrication methods are costly.
A particular example of such prior art methods is U.S. Pat. No. 7,521,017 B2 to Joseph M. Kunze et al. (issued Apr. 21, 2009). This document discloses the application of a laser deposition process (such as LENS) for the fabrication of discontinuously reinforced titanium alloy (DRTi) metal matrix composites. The application and utilization of pre-alloyed, in-situ metal alloy powder compositions is disclosed. Specifically, a Ti alloy powder (such as Ti-6Al-4V) containing about 0-35% (by weight) boron (B) and/or about 0-20% (by weight) carbon (C) additions for forming borides (TiB/TiB2) and/or carbide (TiC) discontinuously reinforced titanium alloy metal matrix composites (DRTi's) as demonstrated with the commercially available Ti-6Al-4V+1.4B and Ti-6Al-4V+1.3B+0.6C compositions is disclosed. Kunze et al. further disclose the application and utilization of powder metallurgy blends containing about 0-40% (by volume) ceramic particle reinforcements such as alumina, silicon carbide, and/or boron carbide with the remaining volume comprising the metal matrix powder such as aluminum or an aluminum alloy, titanium or a titanium alloy, copper or a copper alloy, nickel or a nickel alloy, and/or iron or an iron alloy. The LENS process used in Kunze et al., however, does not achieve a sufficient cooling rate that would result in a desirable finely-dispersed microstructure of ceramic elements dispersed throughout the titanium matrix for high-temperature applications in the latest gas turbine engine designs.
Accordingly, it is desirable to provide improved methods for forming ceramic reinforced titanium alloys, resulting in an improved microstructure. Further, it is desirable to provide such methods that achieve cost savings over prior art methods. Furthermore, other desirable features and characteristics of the invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.